The Jo Cox Foundation, a charity set up by her widower Brendan with money donated following her murder, has been concentrating on spreading her message of unity.
During the event on Sunday at Priory Park, there will be a free market, giving people the chance to swap clothes, toys, games, books and more.
The Great Get Together has encouraged the public to hold street parties and neighbourhood celebrations to boost community spirit and to pay tribute to Jo Cox across the weekend of the anniversary of her death.
Jo Cox was campaigner on issues relating to the Syrian Civil War, and founded and chaired the all-party parliamentary group Friends of Syria.
The 41-year-old mother of two was killed by Mair as she arrived for her weekly surgery in her Batley and Spen constituency in West Yorkshire during the European Union referendum campaign. I think the huge response is because we're tapping into the national mood.
"It's actually a really, really good reason we're encouraging people to come together".
Her husband Brendan Cox, who is behind the idea, has called on the country to unite against hatred on a number of occasions.
As she so poignantly described in her maiden speech: "'We are far more united and have far more in common than that which divides us.' Her warmth, generosity and compassion will be a lasting legacy", he said.
Speaking to CNN's Christiane Amanpour this week, Cox said he wrote the book for those "who wanted to learn more about her - people who felt she stood for something". Sometimes we are familiar with people's faces but might not have met them before.
"And with The Great Get Together, what we've got is a reason to come together that isn't a bad reason".
"Politics at the moment is so divisive".
"Our heart goes out to the people who spent the night hoping their loved ones are safe but probably coming to realise they may not be".
More than one hundred organisations are supporting The Great Get Together, from The Big Lunch, Help for Heroes to Amnesty International, the RNLI to the RSPB as well as the Scouts and the Guides and The Women's Institute.
"We've had a lot of really horrendous things happen in the past 12 months, whether it's the Manchester attack, or the London attack or this horrendous fire this week, but what you see when those frightful things happen is that people do come together and we see the best of community spirit".